package com.jstarcraft.ai.jsat.classifiers.evaluation;

/**
 * Evaluates a classifier based on Mathews Correlation Coefficient
 * 
 * @author Edward Raff
 */
public class MatthewsCorrelationCoefficient extends SimpleBinaryClassMetric {

    private static final long serialVersionUID = 7102318546460007008L;

    public MatthewsCorrelationCoefficient() {
        super();
    }

    public MatthewsCorrelationCoefficient(MatthewsCorrelationCoefficient toClone) {
        super(toClone);
    }

    @Override
    public double getScore() {
        double denom = (tp + fp) * (tp + fn) * (tn + fp) * (tn + fn);
        if (denom <= 1e-16)
            return 0;
        return (tp * tn - fp * fn) / Math.sqrt(denom);
    }

    @Override
    public boolean equals(Object obj) {
        if (this.getClass().isAssignableFrom(obj.getClass()) && obj.getClass().isAssignableFrom(this.getClass())) {
            return true;
        }
        return false;
    }

    @Override
    public int hashCode() {
        return getName().hashCode();
    }

    @Override
    public MatthewsCorrelationCoefficient clone() {
        return new MatthewsCorrelationCoefficient(this);
    }

    @Override
    public String getName() {
        return "Matthews Correlation Coefficient";
    }

}
